Why leave a champion team for a midfielder?

Williams is a very different race team to the one Paddy Lowe achieved great success with in the early 1990s. So why has he left Formula 1's recent dominator to rejoin what is now no more than a plucky independent?

A twinkle in the eye. That subtle signifier of mischief within. It gives Paddy Lowe away as one of the good guys, even as he carries - lightly - the mantle of technical greatness. The warmth of his greeting at Williams's Grove HQ, a readiness to chat. It's disarming in one so accomplished.

This, after all, is the man whose technical leadership (in tandem, it must be noted, with engine boss Andy Cowell) helped Mercedes to a period of consummate domination from 2014-16. And one whose CV encompasses years at Williams during its 1990s glory days, then McLaren when it was last a frontrunner.